seconds of someone’s life—frame by
frame—then playing it backward and
forward until it makes sense.

In March 2015, CRU detectives were
puzzled after a man was found dying on
Goshen Road in Gaithersburg just after
1 a.m. on a Saturday. When a car strikes
a pedestrian with enough force to kill,
the victim’s legs typically are broken at
about the height of the bumper, they
say. This victim’s legs weren’t broken,
which didn’t make sense to the detectives until they discovered that the man,
Osmin de Jesus Montano Carrillo, 35,
had been walking home from a night of
heavy drinking, passed out in the street
and was prone when a teenage driver ran
over him, says Detective Michael Polcsa,
who led the investigation.

The driver—who had also beendrinking—fled. But police quickly iden-tified her as Helen Rommel, then 18, ofLaytonsville. Rommel told investigatorsthat she’d spotted the man passed outin the road at the last instant, too lateto avoid hitting him. As part of theirreconstruction, investigators towedRommel’s 2015 Volkswagen Jetta backto Goshen Road one night, closed thestreet and placed the deceased man’sclothing over boxes approximating hislength and girth. A CRU detective drovethe Jetta along the route Rommel tookin order to determine if the teen couldhave spotted Montano Carrillo lying inthe dark street in time to have avoidedhitting him. Polcsa’s conclusion: Thevictim “was an unavoidable hazard.” Still,Rommel pleaded guilty last yearto driv-ing while impaired by alcohol and failureto immediately return and remain at thescene of an accident involving death. Shereceived a suspended sentence and twoyears of probation.

Increasingly, with the proliferation
of surveillance cameras, CRU investigators are able to find video footage of
fatal collisions. A security camera at the
U.S. Nuclear Regulatory Commission in
Rockville was recording the street below
as two young men, 26-year-old lifelong
friends, got off the Metro at White Flint
and were walking across Rockville Pike
just after 3 a.m. on Oct. 10, 2010. Alejan-dro Roman, 25,of Rockville was drunk
and speeding north on the Pike in a 2010
Acura TXS, when he struck and killed
them, says Detective Barry Robinson,
lead investigator in the case.

Robinson, now 54, studied the video
to see how long it took the two men to
walk between fixed landmarks, such as
streetlights, that were visible in the footage. He measured the distance between
those landmarks to help him calculate
how fast the two men were walking.